Abstract
To observe changes in bone metabolism and associations between it and the development of milk fever, we investigated serum tartrate-resistant acid phosphatase (TRAP) activity at each lactating stage in 83 cows. The animals were from farms A and B, where milk fever occurred rarely, and farms C and D, where it was frequent. On farms A and B, serum TRAP activity was higher at lactation stages than at dry stages. On farm D at all stages it was lower than on the other farms. Apparently, on farm D, inactive bone resorption during the dry stage accounted for frequent occurrences of milk fever. In the dry stage, the level of serum TRAP activity was at almost the same level on farm C as on farms A and B. These findings suggest that, on farm C, frequent occurrence of milk fever resulted not from reduced bone resorption, but from an age factor.
